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Create a constructor in a test case so that it will only be called once

Trying to create a constructor that is called only once in my unit tests

public class ArtistTest extends InstrumentationTestCase{
    private static final String TAG_NAME = "TESTING_SUITE";
    private TestingMusicDAO musicDAO;
    private List<Song> songs;
    private Instrumentation instr;
    MusicService musicService;

    public ArtistTest() throws Exception {
        super();       
        instr = this.getInstrumentation();
        Log.d(TAG_NAME, "Setting up testing songs");
        musicDAO = new TestingMusicDAO(instr.getContext());
        musicService = new MusicServiceImpl(musicDAO);
        musicDAO.getAllSongsFromFile();
        songs = musicDAO.getAllSongs();
        for(Song song : songs)
            Log.d( TAG_NAME, song.toString() );
    }

But I am getting a constructor error when I run the file as Android Junit Test. There is also a stack trace

 junit.framework.AssertionFailedError: Exception in constructor: test0      (java.lang.NullPointerException
 at com.intellimec.ilane.ice.mediaservices.ArtistTest.<init>(ArtistTest.java:17)
 at java.lang.reflect.Constructor.constructNative(Native Method)
 at java.lang.reflect.Constructor.newInstance(Constructor.java:417)
 at junit.runner.BaseTestRunner.getTest(BaseTestRunner.java:118)
 at android.test.AndroidTestRunner.getTest(AndroidTestRunner.java:148)
 at android.test.AndroidTestRunner.setTestClassName(AndroidTestRunner.java:56)
 at   android.test.suitebuilder.TestSuiteBuilder.addTestClassByName(TestSuiteBuilder.java:80)
 at android.test.InstrumentationTestRunner.parseTestClass(InstrumentationTestRunner.java:444)
 at android.test.InstrumentationTestRunner.parseTestClasses(InstrumentationTestRunner.java:425)
 at android.test.InstrumentationTestRunner.onCreate(InstrumentationTestRunner.java:370) 
 at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4382)
 at android.app.ActivityThread.access$1300(ActivityThread.java:141)
 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1294)
 at android.os.Handler.dispatchMessage(Handler.java:99)
 at android.os.Looper.loop(Looper.java:137)
 at android.app.ActivityThread.main(ActivityThread.java:5039)
 at java.lang.reflect.Method.invokeNative(Native Method)
 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
 at dalvik.system.NativeStart.main(Native Method)
 )
 at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:190)
 at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:175)
 at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:555)
 at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1661)
+3


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4 answers


Place the code that you only need to execute once during trial runs into a static initializer. It should only run once when the class is loaded (do not reuse this class).



+2




you can also write your own setUp () method to initialize Music objects once See this page for more details http://www.methodsandtools.com/tools/tools.php?junit



0


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What's in ArtistTest.java:17

?

If it getInstrumentation

just returns private field instr

then it returns null in the call here, causing the NPE to later

0


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Don't use a specific constructor for test cases.

Better to follow the junit paradigm.

use these annotations to initialize any values ​​you need to initialize once per class. i.e. @BeforeClass and @AfterClass Make sure you define whatever you want for class-level initialization

@BeforeClass
public static void setUpBeforeClass() throws Exception {
 //per class attributes initialized here
   instr = this.getInstrumentation();
    Log.d(TAG_NAME, "Setting up testing songs");
    musicDAO = new TestingMusicDAO(instr.getContext());
    musicService = new MusicServiceImpl(musicDAO);
    musicDAO.getAllSongsFromFile();
    songs = musicDAO.getAllSongs();
    for(Song song : songs)
        Log.d( TAG_NAME, song.toString() );
}

@AfterClass
public static void tearDownAfterClass() throws Exception {
 //per class attributes destroyed here
}

for any initialization needed for each method, use the following annotations to tell junit to initialize these values ​​for each test method.

@Before
public void setUp() throws Exception {
 //per method attributes initialized here

}

@After
public void tearDown() throws Exception {
 //per method attributes destroyed here
}

use @Test annotation to mark a method as a test method

i.e.

@Test
public void testMethodx() {
}
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